Compared with conventional cathode ray tube display devices, flat panel display devices have the advantages of light weight, thin thickness, low driving voltage, no flicker or jitter, long service life and so on. The flat panel display devices are mainly classified into active light-emitting display devices and passive light-emitting display devices. For example, Thin Film Transistor-Liquid Crystal Displays (TFT-LCD) are passive light-emitting display devices. With the advantages of stable pictures, realistic images, small radiation, space saving, low energy consumption and so on, the thin film transistor-liquid crystal displays are widely applied in TV sets, mobile phones and other electronic products and have predominated in the field of flat panel display.
In liquid crystal display devices which are passive light-emitting display devices, backlight modules or ambient light are needed to provide light sources for the liquid crystal display devices since liquid crystal display panels themselves are non-luminous. In the prior art, to correctly display color images, a color filter is usually mounted in front (i.e., a light exiting direction) of a backlight module. Thus, after light provided by the backlight module or external environment enters the color filter (CF for short), the color filter may accurately select light within a specific waveband to allow the light to pass therethrough, and reflect or absorb undesired light within other wavebands. Thereby, an observer may receive saturated light of a certain color, and the color image display is finally realized.
In the prior art, absorption type color filters are usually used. That is, a color filter only allows incident light within a specific waveband to pass therethrough and absorbs incident light within other wavebands. For example, a red pixel region allows only red light in the incident light to pass therethrough, while light of other colors in the incident light is absorbed. Thus, on one hand, the transmittance of the incident light is very low (about 30% only); on the other hand, it is likely to result in temperature rise after the color filter absorbs light energy, so that the service life of the color filter is reduced.
In addition, a polarizing sheet is generally provided on a light entering side of a liquid crystal display panel. Light entering the liquid crystal display panel becomes polarized light by using the polarizing sheet, and then image display is realized by the polarized light by virtue of refractivity anisotropy of liquid crystal molecules in the display panel. Majority of polarizing sheets used in the liquid crystal display devices in the prior art are absorption type polarizing sheets. For example, the polarizing sheets will usually absorb about 50% of light in a non-preset polarization direction. Thus, the transmittance of incident light and the utilization ratio of the incident light are further reduced, and it is difficult to enhance the contrast ratio of the display devices, so that it is difficult to ensure the quality of image display.